This invention relates to a phenyl-containing polysiloxane material, and in particular a fiber optic waveguide protected by such a material.
The use of fiber optics for transmitting information has recently received a great deal of attention because of the light weight, security, safety, and electrical isolation that can be obtained with a fiber optic system, and the enormous amount of information that can be transmitted through each fiber of a fiber optic system. Fiber optic systems use a waveguide for transmitting light between a light emitter and a light detector. Waveguides consisting of a variety of materials have been developed. For example, waveguides consisting of a glass core and a glass cladding, a glass cladding and a liquid core, a polymeric core and a polymeric cladding, and a glass core and a polymeric cladding are known.
Typically, a fiber optic waveguide has a buffer coating (or fiber buffer) surrounding it and immediately adjacent to the cladding, to provide mechanical isolation and protection. Additionally, the buffer coating may act as a cladding mode stripper--that is, it permits light being transmitted in the cladding of the fiber to leave the cladding, thereby removing the cladding propagation modes without disturbing the core-supported propagation modes. For a buffer coating to be an effective cladding mode stripper, it should have a refractive index greater than that of the cladding (for glass cladding, greater than about 1.45). It has been proposed to use polysiloxane buffer coatings. See, generally, Cuellar et al., "Static Fatigue Lifetime of Optical Fibers in Bending," presented at the First Military Fiber Optics and Communications Conference, Washington, D.C., Mar. 16-19, 1987, and Imai, "Silicone Coating Material for Optical Fibers," Toshiba Review 38, 171-174 (1983). One polysiloxane which has been used is polydimethylsiloxane, a readily available material, but with a relatively low refractive index of about 1.40. Phenylated polysiloxanes have also been proposed as buffer coatings. Compared to polydimethylsiloxane, they possess the advantage of higher refractive index (typically greater than 1.45).
Another important function of the buffer coating is to protect the fiber against static fatigue. Further, the buffer coating must be readily stripped off the fiber, leaving behind a clean, exposed but undamaged fiber, as would be necessary in preparing the fiber for making splices, joints, or terminations.
This invention provides a polysiloxane buffer coating which has high refractive index, confers high static fatigue resistance to an optical fiber, and is readily stripped off the fiber.